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09-08-2019, 07:43 PM | #1 |
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Join Date: Mar 2019
Posts: 31
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Short circuit issues. Where to start
I am new to Ford Model A’s. Most of my time has been around British cars. I am having a short problem which is draining the battery. Main fuse by starter motor gets excessively hot as did the horn before I disconnected. There is an aftermarket fuse box which I need to disconnect from firewall since it doesn’t open from the front. My question is are there any usual spots I should look for shorts to be happening? This is a 1930 Model A coupe with cowl lights. This car has not been restored. Rubs and drives well when battery has enough charge to start. This car is still a 6 volt system. Need to find a 6 volt test light. Any help appreciated.
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09-08-2019, 08:07 PM | #2 |
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Location: Coatesville, Pa
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Re: Short circuit issues. Where to start
A 12 volt test light will work just fine. Just a little dim. Or use a multimeter. Disconnect one set of wires at a time. Headlights, tail lights, brake lights, ammeter etc. until you find the one causing the problem.
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09-08-2019, 10:09 PM | #3 |
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Re: Short circuit issues. Where to start
If the horn is getting hot, then it's likely shorted to ground.
What does the ammeter read with the key off? |
09-08-2019, 10:10 PM | #4 |
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Re: Short circuit issues. Where to start
The biggest problem is we don't (and it seems you don't ) exactly how the car was wired.
If it were me I would turn everything off. I would disconnect the output of a terminal on the fuse panel. Connect one lead of a test lamp or meter to that point. The other lead to the wire just disconnected. The the lamp or meter will indicate voltage if there is a short.
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09-09-2019, 10:04 AM | #5 |
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Join Date: May 2010
Location: Largo Florida
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Re: Short circuit issues. Where to start
If you are used to Lucas Electrics then the Model A is childs play.
As in any electrical system, A meter or test light [ 12v light will work fine] across a load [ battery, fuse, etc] will show if there is a draw or not. From your post I think the first to disconnect/check is the horn |
09-09-2019, 02:01 PM | #6 |
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Re: Short circuit issues. Where to start
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09-09-2019, 03:24 PM | #7 |
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Location: Southern California
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Re: Short circuit issues. Where to start
See attached article.
Tom Endy |
09-09-2019, 05:33 PM | #8 | |
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Join Date: Jun 2014
Location: Melbourne, Australia
Posts: 7,496
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Re: Short circuit issues. Where to start
Quote:
As for the OP, I'd go around all of the circiuts, disconnecting one at a time (in this one, I'd statrt with the horn) and see which one results in no blown fuse. Then I'd trace the circuit right through, inch by inch, looking for the short.
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09-10-2019, 03:55 PM | #9 |
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Location: Kentucky
Posts: 502
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Re: Short circuit issues. Where to start
I have both British cars and A's Lucas is fine... it boils down to clean grounds and good clean connections to battery etc. I have a owned a MGA for 20 years and not a single electrical failure except batteries wore out..
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